Van Hise — Metamorjphism of Rocks and Rock Flow age. 85 



lated. However, the granulated and recrystallized rocks are 

 not separated sharply from each other, but, on the contrary, 

 there is every gradation between the two. If in the altered 

 sedimentary rocks one passes from a place of granulation to 

 one of recrystallization, he finds that recrystallization of the 

 matrix begins while granulation of the larger particles is 

 still going on. Whether granulation or recrystallization is the 

 dominant process in a given place in the zone of flowage de- 

 pends upon many factors. Some of these factors are the 

 character of the material, water content, temperature, pressure, 

 and rapidity of deformation. Refractory minerals are favor- 

 able to granulation ; mobile minerals are favorable to recrys- 

 tallization. Absence of water is favorable to granulation; 

 presence of water is favorable to recrystallization. Low 

 temperature is favorable to granulation ; high temper- 

 ature is favorable to recrystallization. The less the pres- 

 sure the more likely is the deformation to be accomplished 

 by granulation. The greater the pressure the more likely 

 is the deformation to be accomplished by recrystalliza- 

 tion. To a certain point, the more rapid the deforma- 

 tion the more likely is the adjustment to be by granula- 

 tion. The slower the deformation the more likely is the re- 

 adjustment to be by recrystallization. 



Some of the more characteristic features of the crystalline 

 schists are their evenness of grain, and the similar crystal- 

 lographic orientation of the autbigenic particles of some of the 

 minerals. 



In the recrystallization of rocks in the deep-seated zone 

 adjustment may not lag far behind the disturbing forces. 

 However, in most cases there is apparently some lag. In the 

 most regularly laminated of the crystalline schists a close ex- 

 amination usually shows a slightly undulatory extinction, and 

 therefore a state of strain in the minerals, showing that recrys- 

 tallization has not exactly kept pace with deformation, or else 

 that they have been somewhat deformed nearer the surface 

 since recrystallization. 



It is concluded that the development of the crystalline 

 schists is to be explained as a process of chemical reaction in- 

 duced by mechanical action, resulting in the constant solution 

 and deposition of the material so as to accommodate it to the 

 changing form of the mass. 



Comparative energy required for deformation in the three 

 zones, of fracture, fracture and floicage, and flowage. — The 

 energy required for deformation in the three zones of fracture, 

 fracture and flowage, and flowage, is discussed, and the conclu- 

 sion is reached that the amount of work done, in order to pro- 

 duce the same mass deformation of the rocks, increases down 



